An integrated approach for phycoremediation of municipal wastewater and production of sustainable transportation fuel using oleaginous Chlorella sp

The explosion in urban population are increasing burdens on water and energy systems, which ultimately release harmful pollutants such as wastewater and toxic gases into the natural ecosystems. In order to eliminate these pollutants, the production of vehicular quality biodiesel along with the phycoremediation of wastewater using two different Chlorella species (Chlorella minutissima and Chlorella sorokiniana) was investigated. Both the Chlorella sp., due to their stress tolerance behavior showed higher growth rate, lipid content and biomass productivity, when cultivated in wastewater than in control. Chlorella sorokiniana exhibited 19.14% higher lipids than Chlorella minutissima, when cultivated in wastewater. The fatty acid methyl esters (FAMEs)/biodiesel profiling has shown the decrease in poly unsaturated fatty acids (PUFAs) with enhancement in saturated fatty acids (SFAs) and oleic acid content. The physical properties of biodiesel derived from Chlorella sorokiniana, exceeded the existing biodiesel standards for USA and Europe e.g. the biodiesel (89.23 ± 0.21%; w/w of lipids) obtained from Chlorella sorokiniana, grown in wastewater was having lower cold filter plugging point (−6.22 °C), higher cetane number (47) and average oxidative stability (3.43 h). During the process, these Chlorella species have also removed total phosphate (TP), total nitrogen (TN), chemical oxygen demand (COD) and total organic carbon (TOC) from wastewater. The removal efficiency of TOC was found to be 95% and 98% by Chlorella minutissima and Chlorella sorokiniana respectively. Overall, Chlorella sorokiniana grown in wastewater was found to be a better candidate for the biodiesel production together with phycoremediation of wastewater.